cd: Add a class for the build mode.

I found that cd-comment.tpl.php does not put a class for the build mode. This will make it hard to do custom css.
What about

<?php
$class = 'clear-block comment cd-build_mode-'. $comment->build_mode;
if (isset($comment->status) && $comment->status == COMMENT_NOT_PUBLISHED) {
  $class .= ' comment-unpublished';
}
if ($new != '') {
  $class .= ' new';
}
?>
<div class="<?php print $class; ?>">
<div class="content"><?php print $content; ?></div></div>

It would be great if we can agree on a reasonable logic quickly, so I don't have to theme override.
The class stuff could be in a preprocess function, instead of in the template itself.